There are brilliant advertising campaigns, and then there are excellent ways to lose your job in public relations. This is an example of the latter.
On March 31, 1940, the Franklin Institute declared that the world was ending as a promotion for their new planetarium show on cosmic apocalypses. To advertise this exhibit, Franklin Institute press agent William Castellini passed on this thrilling copy to the announcers at the Philadelphia radio station KYW:
Your worst fears that the world will end are confirmed by astronomers of Franklin Institute, Philadelphia. Scientists predict that the world will end at 3 P.M. Eastern Standard Time tomorrow. This is no April Fool joke. Confirmation can be obtained from Wagner Schlesinger, director of the Fels Planetarium of this city.
Despite airing the ad after a Jack Benny radio show discussing such topics as the end times and Orson Welles' War of the Worlds stunt, emergency lines were swamped with calls from confused citizens. Castellini offered the feeble explantation that he thought the folks at KYW were in on the stunt. In the end, this snafu cost him his job at the Institute.
For another occasion the apocalypse prematurely hit the airwaves, see the time World War III began during a Partridge Family song.